Michael Heseltine and his wife Anne purchased Thenford house in 1976, and over the next twenty five years they set about restoring over 40 acres of woodland. In order to help with the replanting programme the Heseltines sought advice from some of the leading horticultural leaders of the time, including Lanning Roper, Sir Harold Hillier, Roy Lancaster and Keith Rushforth.

The eighteenth century woodland had been grown for its commercial value. The Heseltines widened the choice of trees and shrubs and thus laid the foundations of the present collection. It was around the turn of the century and free of the responsibilities of the government that the Heseltines decided to create a range of ornamental features and seriously enhance the quality of the collection.

The arboretum, now spread out over seventy acres, features a collection of more than three thousand different trees and shrubs, together with extensive herbaceous borders, water gardens, an alpine trough garden, a sculpture garden, a rose garden and a rill as well as a collection of over 600 different types of snowdrops. The medieval fish ponds, their interconnecting canal and the existing lake have been restored and two new ones have been added. An eighteenth century avenue of mature yews has been cleared of self seeded shrubs and saplings, and returned to its former grandeur.